U.S. patent application number 12/450106 was filed with the patent office on 2010-02-04 for relay connection unit mounted in vehicle.
This patent application is currently assigned to AUTONETWORKS TECHNOLOGIES, LTD. Invention is credited to Yoshikazu Isoyama.
Application Number | 20100031106 12/450106 |
Document ID | / |
Family ID | 39863805 |
Filed Date | 2010-02-04 |
United States Patent
Application |
20100031106 |
Kind Code |
A1 |
Isoyama; Yoshikazu |
February 4, 2010 |
RELAY CONNECTION UNIT MOUNTED IN VEHICLE
Abstract
A Relay connection unit which is connected with a plurality of
buses and relays a message to a different bus. The relay connection
section comprises a data check section for detecting an error in a
data section of a received message, a storage section for storing
set data or/and the previously sent data for message rewriting use
for each ID (identifier) attached to the message, and a data
rewrite portion for rewriting the data section of the message in
which the error is detected into the set data or the previously
sent data stored in the storage section.
Inventors: |
Isoyama; Yoshikazu;
(Yokkaichi-shi, JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 320850
ALEXANDRIA
VA
22320-4850
US
|
Assignee: |
AUTONETWORKS TECHNOLOGIES,
LTD
YOKKAICHI-SHI
JP
SUMITOMO WIRING SYSTEMS, LTD
YOKKAICHI-SHI
JP
SUMITOMO ELECTRIC INDUSTRIES, LTD
OSAKA-SHI
JP
|
Family ID: |
39863805 |
Appl. No.: |
12/450106 |
Filed: |
March 28, 2008 |
PCT Filed: |
March 28, 2008 |
PCT NO: |
PCT/JP2008/056039 |
371 Date: |
September 11, 2009 |
Current U.S.
Class: |
714/746 ;
714/E11.023; 714/E11.024 |
Current CPC
Class: |
H04L 2012/40273
20130101; H04L 2012/40215 20130101; H04L 12/4625 20130101; H04L
2001/0094 20130101; H04L 1/0061 20130101; H04L 12/40169
20130101 |
Class at
Publication: |
714/746 ;
714/E11.023; 714/E11.024 |
International
Class: |
G06F 11/07 20060101
G06F011/07 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2007 |
JP |
2007-098957 |
Claims
1-6. (canceled)
7. A relay connection unit, to be mounted on a car, which is
connected to a plurality of buses to which said relay connection
unit relays a message, comprising: a data check section detecting
an error in a data section of a received message; a storage section
storing set data or/and previously sent data for message-rewriting
use for each identifier attached to said message; and a data
rewrite portion rewriting said data section of said message in
which said error has been detected by said data check section into
said set data or said previously sent data stored in said storage
section.
8. The relay connection unit to be mounted on a car according to
claim 7, further comprising a sending/receiving section relaying
said message by using a cut-through method of starting transmission
at a time when said identifier of said message is received, before
said data check section checks said data section of said received
message entirely.
9. The relay connection unit to be mounted on a car according to
claim 7, wherein said storage section storing said set data or/and
said previously sent data for message-rewriting use is a RAM; said
storage section has a ROM storing a routing table specifying a
relay destination of said received message and break point
discrimination data; and said data check section has an error
detection portion and a data rewrite portion and is connected to
said RAM and said ROM; said error detection portion of said data
check section checks an error in said data section of said message;
and said data rewrite portion rewrites said data section of said
message in which said error has been detected.
10. The relay connection unit to be mounted on a car according to
claim 9, wherein said previously sent data stored in said RAM
consists of a latest previously sent data stored by rewriting said
previously sent data each time said message is sent.
11. The relay connection unit to be mounted on a car according to
claim 10, wherein said data section of said message to be checked
by said data check section consists of a plurality of sub-data; and
break point discrimination data indicating a break point of each
sub-data is stored in said RAM; said data check section detects a
top bit of sub-data in which an error has been detected by said
error detection portion thereof from said break point
discrimination data stored in said RAM; and said data rewrite
portion thereof rewrites said sub-data into said set data or said
previously sent data from said top bit of said sub-data; and said
rewritten data is stored in said RAM.
12. The relay connection unit to be mounted on a car according to
claim 9, wherein said RAM stores both said set data and said
previously sent data for message-rewriting use; and for each
identifier of said message or/and each sub-data, said data rewrite
portion selects said set data or said previously sent data as a
value to be rewritten.
13. The relay connection unit to be mounted on a car according to
claim 10, wherein said RAM stores both said set data and said
previously sent data for message-rewriting use; and for each
identifier of said message or/and each sub-data, said data rewrite
portion selects said set data or said previously sent data as a
value to be rewritten.
14. The relay connection unit to be mounted on a car according to
claim 11, wherein said RAM stores both said set data and said
previously sent data for message-rewriting use; and for each
identifier of said message or/and each sub-data, said data rewrite
portion selects said set data or said previously sent data as a
value to be rewritten.
Description
TECHNICAL FIELD
[0001] The present invention relates to a relay connection unit to
be mounted on a car. More particularly the present invention
relates to the relay connection unit rewriting the data of a
message in which an error has been detected into a suitable data to
relay the message as a complete message.
BACKGROUND ART
[0002] A communication system to be mounted on a car is
conventionally adopted in which communication lines (hereinafter
referred to as bus) connected to electronic control units (ECU:
Electronic Control Unit) controlling the operation of appliances
mounted on the car are connected with a relay connection unit such
as a gateway to send and receive messages among the ECUs.
[0003] In recent years, with an increase in the function of the
car, the number of the ECUs has increased and the number of
messages to be sent and received among the ECUs has rapidly
increased. Therefore there is a demand that messages are
efficiently sent and received among the ECUs and that a
communication load factor of the bus is decreased.
[0004] To decrease the communication load, it is conceivable that
stopping the transmission of an incomplete message in which an
error has occurred is effective. In this case, an ECU to which the
message is to be sent is incapable of periodically receiving the
message.
[0005] The error message is generated in a case in which an
improbable sudden change has occurred in data relating to a car
speed, temperature, illuminance, rainfall, and the like; a case in
which data exceeds an ordinary set range; and a case in which an
improbable combination is made among a plurality of data.
[0006] Thus in Japanese Patent Application Laid-Open No. 2002-16614
(patent document 1), there is proposed the gateway which does not
transfer an incomplete message in which an error has occurred.
[0007] But in the gateway proposed in the patent document 1,
whether the message is to be transferred is determined after
judging whether an error has occurred by checking the content of
the message. Therefore unless the message is entirely received, it
is impossible to determine whether the message is to be
transferred.
[0008] When it is determined that the message is not transferred,
an ECU at a reception side is incapable of periodically receiving
the message periodically sent and received among the ECUs.
[0009] Further the gateway is capable of dealing with a store &
forward method of starting transmission after the message is
entirely received, but is incapable of dealing with a cut-through
method, having a favorable transfer efficiency, of determining a
destination to which the message is transferred when the ID
(identifier) is received before the message is entirely received
and starting transmission. Thus the gateway is capable of
decreasing the communication load factor of the bus, but has room
for improvement in sending and receiving the message
efficiently.
[0010] Patent document: Japanese Patent Application Laid-Open No.
2002-16614
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0011] The present invention has been made in view of the
above-described problems. It is an object of the present invention
to provide a relay connection unit capable of rewriting an
incomplete message having an error, sending the message as a
complete message, and efficiently transferring the complete
message.
Means for Solving the Problem
[0012] To solve the above-described problem, the present invention
provides a relay connection unit, to be mounted on a car, which is
connected to a plurality of buses to which the relay connection
unit relays a message. The relay connection unit has a data check
section detecting an error in a data section of a received message;
a storage section storing set data or/and previously sent data for
message-rewriting use for each identifier attached to the message;
and a data rewrite portion rewriting a data section of the message
in which the error has been detected by the data check section into
the set data or the previously sent data stored in the storage
section.
[0013] The storage section storing the set data or/and the
previously sent data for message-rewriting use is a RAM; the
storage section has a ROM storing a routing table specifying a
relay destination of the received message and break point
discrimination data; and the RAM and the ROM are connected to the
data check section and the data rewrite portion.
[0014] When the power is turned on, the break point discrimination
data of the ROM is copied to the RAM from the ROM. Thereafter the
break point discrimination data is merely stored in the RAM and
merely accessed to the RAM.
[0015] In the relay connection unit having the above-described
construction, the set data or/and the previously sent data for
message-rewriting use are stored in the storage section (RAM) for
each ID of the message. Therefore with reference to the set data or
the previously sent data having an ID coincident with the ID of a
message in which an error has been detected, data can be
rewritten.
[0016] When the data check section detects an error of the received
message, the data rewrite portion rewrites the data section of an
incomplete message in which the error has been detected into the
set data or the previously sent data stored in the RAM, so that the
received message is sent to the necessary bus as a complete
message. Thereby it is possible to prevent the transmission of an
incomplete message including the error. Further because the
transfer of the message is not stopped, an ECU which is to receive
messages periodically is capable of periodically receiving normal
messages.
[0017] As the standard for detecting the error of the message, for
example, the data check section is provided with the following
standards:
[0018] (1) In the case where the communication protocol of the
communication system is CAN and in the case where it is checked at
a CRC that signals having the same level are successive in a
message by 6 bits and that a staff error of not receiving the data
of the message has occurred.
[0019] (2) A case in which data indicates an improbable sudden
change. For example, a case in which an inside temperature and an
outside temperature detected by a temperature sensor indicate an
improbable sudden change, and a case in which a value detected by a
car speed sensor changes more than a certain value with respect to
a value detected thereby previously.
[0020] (3) A case in which a detected value is more than an upper
limit value or less than a lower limit value. For example, a case
in which the outside temperature detected by the temperature sensor
exceeds 70.degree. C. or is a default value.
[0021] (4) A case in which an improbable combination is made among
a plurality of data. For example, only one tire reversely rotates
in the rotational frequency of rotations of four wheels.
[0022] The relay connection unit of the present invention has a
sending/receiving section relaying the message by using a
cut-through method of starting transmission at a time when the ID
of the message is received, before the data check section checks
the data section of the received message entirely.
[0023] That is, the store & forward method of determining
whether it is necessary to transfer the message after confirming
whether the message has an error by checking the entire message
data is not adopted in the present invention, but in the present
invention, the cut-through method of starting transmission with the
data check section checking an error of the message when the ID of
the message is received is adopted. In this method, if an error is
detected, the error is corrected and the corrected message is sent.
Therefore it is possible to relay the message at a high speed.
[0024] As a method of transferring the message, it is possible to
adopt the store & forward method of starting transmission after
receiving a message entirely to send a message by correcting the
data of the message having an error. But the cut-through method is
preferable to send the message at a high speed.
[0025] The previously sent data stored in the RAM consists of a
latest previously sent data stored by rewriting the previously sent
data each time a message is sent.
[0026] By adopting the latest previously sent data to rewrite the
error data, it is possible to minimize an error between correct
sent data and the latest previously sent data.
[0027] When the region of the RAM is large, entire sent data or
data previously sent several times may be stored to adopt the
latest sent data.
[0028] It is preferable that the data section of the message to be
checked by the data check section consists of a plurality of
sub-data; and break point discrimination data indicating a break
point of each sub-data is stored in the RAM; that the data check
section detects a top bit of sub-data in which an error has been
detected by the error detection portion thereof from the break
point discrimination data stored in the RAM; that the data rewrite
portion thereof rewrites the sub-data into the set data or the
previously sent data from the top bit of the sub-data; and that the
rewritten data is stored in the RAM.
[0029] In the above-described construction, the entire data section
of the message in which the error has been detected is not
rewritten, but only the sub-data subsequent to the sub-data in
which the error has been detected is rewritten into the set data or
the previously sent data. Sub-data previous to the sub-data in
which the error has been detected is sent without rewriting it.
Therefore the message can be efficiently sent.
[0030] When the data rewrite portion executes rewriting from the
bit where the error has occurred, data before rewriting and data
after rewriting are mixedly present in one sub-data. Thus there is
a possibility that an inappropriate data is generated. But in the
present invention, the sub-data in which the error has occurred is
entirely rewritten. Therefore it is possible to securely correct
the sub-data in which the error has occurred into the complete
data.
[0031] In the break point discrimination data, the range of each
sub-data is expressed by making bits having an equal value
successive. The value of the bit is changed at a break point
position of the sub-data.
[0032] For example, when the break point discrimination data is
expressed as "1110011110 . . . ", it means that a range from a
first bit to a third bit in which "1" is successive is a first
sub-data, that a fourth bit and a fifth bit with "0" being
successive are a second sub-data, and that a range from a sixth bit
to a ninth bit with "1" being successive is a third sub-data.
Therefore when an error is detected at an eighth bit, with
reference to the break point discrimination data, it is detected
that a sub-data including the eighth bit starts from the sixth bit,
and data subsequent to the sixth bit is rewritten into the set data
or the previously sent data.
[0033] The break point discrimination data may be provided for each
sub-data to express a bit corresponding to the sub-data as "1" and
a bit uncorresponding to the sub-data as "0". In this case, the
break point discrimination data is stored in the storage section by
expressing the break point discrimination data for detecting the
range of the first sub-data as "1110000000 . . . ", by expressing
the break point discrimination data for detecting the range of the
second sub-data as "0001100000 . . . ", and by expressing the break
point discrimination data for detecting the range of the third
sub-data expressed as "0000011110 . . . ".
[0034] It is preferable that the RAM stores both the set data and
the previously sent data for message-rewriting use; and that for
each ID of the message or/and each sub-data, the data rewrite
portion selects the set data or the previously sent data as a value
to be rewritten.
[0035] In the above-described construction, in dependence on the
kind of data, the data rewrite portion is capable of selecting the
set data or the previously sent data as the value to be rewritten.
Thereby the data rewrite portion is capable of rewriting the data
of the message in which the error has been detected into
appropriate data.
[0036] For example, when the data of the message relates to door
locking, a key confirmation result, a shift state, and the like, it
is preferable to rewrite the message in which the error has been
detected into the data set in advance. In the case of data relating
to a car speed, temperature, an illuminance, a rainfall, and the
like, it is preferable to rewrite the message in which the error
has been detected into the previously sent data.
[0037] That is, a message relating to safety such as the door
locking is rewritten into data in which importance is attached to
safety, when the message has an error. In the case of a message
indicating a car speed, temperature, an illuminance, and the like
whose content does not suddenly change, the message in which an
error has occurred is rewritten into the previously sent data to
maintain the content of the message by reflecting the content of
the message sent latest.
EFFECT OF THE INVENTION
[0038] As described above, in the present invention, when the data
check section detects an error of the received message, the data
rewrite portion rewrites the data section of the incomplete message
in which the error has been detected into the set data or the
previously sent data stored in the RAM, so that the received
message is sent to the necessary bus as the complete message.
Thereby it is possible to prevent the incomplete message, namely,
the useless message including the error from being sent.
[0039] The store & forward method of determining whether it is
necessary to transfer the message after checking the entire data
section of the message is not adopted in the present invention, but
in the present invention, the cut-through method of starting
transmission when the ID of the message is received is adopted to
relay the message with an error in the data section of the message
being corrected. Therefore it is possible to relay the message at a
high speed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 shows a communication system, to be mounted on a car,
in which a relay connection unit of a first embodiment of the
present invention is used.
[0041] FIG. 2 shows the format of a message.
[0042] FIG. 3(A) shows a routing table storage portion; and FIG.
3(B) shows a break point discrimination data storage portion.
[0043] FIG. 4 shows data for rewriting use of a data storage
portion.
[0044] FIG. 5 is a construction view showing a correlation in data
processing to be executed inside the relay connection unit.
[0045] FIG. 6 is a flowchart of message transfer processing to be
executed by the relay connection unit.
[0046] FIG. 7 shows the flow of data when an error is not detected
in a message.
[0047] FIG. 8 shows the flow of data when an error is detected in a
message.
[0048] FIG. 9 shows data for rewriting use in a second
embodiment.
EXPLANATION OF REFERENCE NUMERALS AND SYMBOLS
[0049] 10: communication system to be mounted on car [0050] 11: bus
[0051] 20: relay connection unit [0052] 23: CPU [0053] 24-1, 24-2:
ROM [0054] 25: RAM [0055] 26: comparison computation section [0056]
27: data check section [0057] 28: data rewrite portion [0058] 29:
error detection portion [0059] 30: ECU (Electronic Control Unit)
[0060] D: data for rewriting use [0061] D1: set data [0062] D2:
previously sent data [0063] D3: break point discrimination data
[0064] M: message [0065] MD: data section [0066] SD: sub-data
[0067] T: routing table
BEST MODE FOR CARRYING OUT THE INVENTION
[0068] The embodiments of the present invention are described below
with reference to the drawings.
[0069] FIGS. 1 through 7 show the first embodiment of the present
invention.
[0070] In a communication system 10 of the first embodiment to be
mounted on a car (hereinafter referred to as communication system
10), communication lines (buses) CAN1, CAN2 using CAN as its
communication protocol are connected to each other via a relay
connection unit (gateway) 20 to construct a communication network.
A plurality of ECUs 30 (electronic control units) is connected to
each of the CAN 1, CAN 2. Appliances, switches, sensors, and the
like to be controlled by the ECUs 30 are connected thereto, but not
shown in the drawings.
[0071] As shown in FIG. 1, the relay connection unit 20 is
connected to the CAN 1 and CAN 2 via a receiving section 21 and a
sending section 22. The receiving section 21 and the sending
section 22 are connected to a CPU 23. The CPU 23 is connected to a
storage section K shown in FIG. 3. The storage section K has a ROM
24-1 consisting of an identifier storage portion, a ROM 24-2
consisting of a break point discrimination data storage portion,
and a RAM 25 consisting of a data storage portion.
[0072] As shown in FIGS. 4 and 5, the CPU 23 has a comparison
computation section 26 determining whether it is necessary to relay
a message and determining a bus through which the message is to be
relayed with reference to a routing table T stored in the ROM 24-1
and a data check section 27 composed of an error detection portion
29 detecting an error of the message which is to be sent through
the CAN determined by the comparison computation section 26 and a
data rewrite portion 28 rewriting the message in which the error
has been detected with reference to data D for rewriting use stored
in the RAM 25.
[0073] As a transfer method, the comparison computation section 26
adopts a cut-through method of starting to send a message before
the comparison computation section 26 receives the entire message,
when it receives the ID of the message and determines a destination
to which the message is to be sent.
[0074] The error detection portion 29 checks whether the errors
described above at (1) through (4) have occurred at a data section
of the message which is described later. For example, the error
detection portion 29 checks whether there is the staff error in the
CRC as described in (1), whether data indicates the improbable
sudden change as described in (2), whether data exceeds the set
reference value as described in (3), and whether the improbable
combination is made among a plurality of data as described in (4).
When an error is detected, the data rewrite portion 28 rewrites the
data section of the message.
[0075] As shown in FIG. 3(A), the ROM 24-1 of the storage section K
stores the routing table indicating the correlation between the
identifier (ID) and the buses (CAN 1, CAN 2 through which the
message is sent. As shown in FIG. 3(B), the ROM 24-2 stores the
identifier, a DLC, and the break point discrimination data. As
shown in FIG. 4, the RAM 25 stores the data D for rewriting use.
The data D for rewriting use includes a set data D1 for rewriting
use, a previously sent data D2 for rewriting use, and a break point
discrimination data D3 provided for each ID of the message.
[0076] When a power is turned on, the break point discrimination
data of the ROM 24-2 is copied to the RAM 25. Thereafter the break
point discrimination data is stored in the RAM. Thereby it is
possible to obtain the break point discrimination data by only an
access to the RAM.
[0077] The set data D1 of the RAM 24 for rewriting use and the
previously sent data D2 thereof for rewriting use are the data for
rewriting the message in which an error has been detected. The set
data D1 is set in advance and has a constant value, whereas the
previously sent data D2 is the data previously sent and rewritten
each time the message is sent. The RAM 25 stores only the latest
previously sent data for each ID.
[0078] Either the set data D1 or the previously sent data D2 is
stored for each ID.
[0079] The set data D1 for rewriting use is stored for the data
relating to a door locking, a key confirmation result, a shift
state, and the like.
[0080] The previously sent data D2 for rewriting use is stored for
the data relating to a car speed, parking brake information,
temperature, an illuminance, a rainfall, and the like.
[0081] The break point discrimination data D3 is the data for
discriminating a break point of each sub-data described at the data
section of the message, as described later. The break point
discrimination data D3 makes it possible to recognize the range of
the data section of the message in which each sub-data is
described. In rewriting the message in which the error has
occurred, a data-rewriting range is determined with reference to
the break point discrimination data D3.
[0082] In the break point discrimination data D3, the range of each
sub-data is expressed by making bits having an equal value
successive. The value of the bit is changed at a break point
position of the sub-data.
[0083] For example, as schematically shown in FIG. 2, when a data
section MD of a message M (ID100) is composed of a first sub-data
SD1 (10 bits) relating to a car speed, a second sub-data SD2 (four
bits) relating to temperature, and a third sub-data SD3 (two bits)
relating to parking brake information . . . in the order of the
first sub-data SD1, the second sub-data SD2, and the third sub-data
SD3, the break point discrimination data D3 is expressed as
"11111111110000110 . . . ", as shown in FIG. 4.
[0084] It can be recognized from the break point discrimination
data D3 that in the data section of a message having an ID of 100,
the range from the first bit to the tenth bit in which "1" is
successive is a first sub-data SD1; that the range from the 11th
bit to the 14th bit in which "1" is switched to "0" with "0" being
successive is a second sub-data SD2; and that the 15th bit and the
16th bit in which "0" is switched to "1" with "1" being successive
is a third sub-data SD3.
[0085] The message M sent and received via the buses in the
communication system 10 of the first embodiment is composed of a
format, as schematically shown in FIG. 2. The ID is described in an
arbitration field. The data section MD is composed of a plurality
of sub-data SD relating to different information.
[0086] An SOF (start of frame) indicates the start of the message.
A DLC (data length code) indicates the length of the data section.
A CRC indicates a field for checking an error in the transmission
of the message.
[0087] The message transfer processing which is executed by the
relay connection unit 20 of the communication system 10 to be
mounted on a car is described below with reference to FIGS. 5 and
6.
[0088] Initially when a power is turned on, the break point
discrimination data of the ROM 24-2 is copied to the RAM 25.
[0089] When the receiving section 21 of the relay connection unit
20 receives a message (step S1 of FIG. 6), the comparison
computation section 26 of the CPU 23 determines whether it is
necessary to transfer the message and the bus through which the
message is to be sent with reference to the routing table T, shown
in FIG. 3(A), which is stored in the ROM 24-1 (step S2 of FIG.
6).
[0090] Thereafter the error detection portion 29 of the data check
section 27 of the CPU 23 checks whether the message to be sent has
an error (step S3 of FIG. 6). A message not to be sent is
discarded.
[0091] When the error detection portion 29 does not detect an
error, the message is sent to a necessary CAN via the sending
section 22, as shown in FIG. 7 (steps S4, S5 of FIG. 6).
[0092] When the error detection portion 29 detects an error and
when the data section of the received message is to be rewritten
into the previously sent data D2, the message is sent to the
necessary CAN via the sending section 22, as described above, and
the message to be sent is written to the RAM 25 as the previously
sent data D2 to update the previously sent data as the latest
previously sent data (step S5 of FIG. 6).
[0093] On the other hand, when the error detection portion 29
detects that the message has an error, as shown in FIG. 8, the data
rewrite portion 28 rewrites the data section of the message (step
S6 of FIG. 6). At this time, with reference to the break point
discrimination data D3, sub-data of the data section where the
error has occurred is detected to rewrite bits in the range from a
top bit of the sub-data in which the error has occurred to a last
bit of the data section as the set data D1 for rewriting use or the
previously sent data D2 for rewriting use.
[0094] For example, when the data section of a message having an ID
of 100 is expressed as "10101010111111 . . . " and when an error is
detected at the 14th bit to which the same bit is successive six
times, with reference to the break point discrimination data D3
shown in FIG. 4, it is detected that the 14th bit is included in
the second sub-data starting from the 11th bit, and the bits
subsequent to the 11th bit which is the top bit of the second
sub-data are rewritten from "1111 . . . " into the previously sent
data D2, having the ID of 100, which is expressed as "0011 . . . ".
The previously sent data D2 having the ID of 100 shown in FIG. 4 is
expressed as "aacc . . . " by a hexadecimal notation. The
above-described message is rewritten by data in a necessary range
of "1010101011001100 . . . " which is expressed by a binary
notation changed from "aacc . . . ".
[0095] Thereby the message in which the error has occurred is
rewritten into a complete message which is sent to the necessary
bus via the sending section 22 (step S7 of FIG. 6), as shown in
FIG. 8.
[0096] In the above-described construction, when the error
detection portion 29 detects the error of the message received by
the data check section 27, the data section of the message in which
the error has been detected is rewritten into the set data D1 or
the previously sent data D2 stored in the RAM 25, so that the
received message is sent to the necessary bus as the complete
message. Thereby it is possible to prevent the transmission of an
incomplete message including the error, namely, a useless
message.
[0097] Whether transfer is necessary or not is not determined after
checking whether the message has an error, but the error of the
message is corrected on the assumption that the message is
transferred. Therefore it is possible to start to send the message
before the message is entirely received and efficiently send the
message by using the cut-through method.
[0098] Further the data section of the message in which an error
has been detected is not entirely rewritten, but only the sub-data
subsequent to the sub-data in which the error has been detected is
rewritten into the set data D1 or the previously sent data D2. The
sub-data previous to the sub-data in which the error has been
detected is sent without rewriting it. Therefore the message can be
efficiently sent.
[0099] When the data rewrite portion executes rewriting from the
bit where the error has occurred, data before rewriting and data
after rewriting are mixedly present in one sub-data. Thus there is
a possibility that an inappropriate data is generated. But in the
present invention, the sub-data in which the error has occurred is
entirely rewritten. Therefore it is possible to securely correct
the sub-data in which the error has occurred into the complete
data.
[0100] FIG. 9 shows the second embodiment.
[0101] The data of the second embodiment for rewriting use stored
in the RAM 25 is different from that of the first embodiment. The
set data D1, the previously sent data D2, and the break point
discrimination data D3 are provided for each sub-data.
[0102] In detail, in the break point discrimination data D3, the
bit corresponding to given sub-data is "1", whereas the bit
uncorresponding to the given sub-data is "0". The break point
discrimination data for discriminating the first sub-data SD1 of
the first embodiment is expressed as "11111111110000000 . . . ".
The break point discrimination data for discriminating the second
sub-data SD2 is expressed as "00000000001111000 . . . ". The break
point discrimination data for detecting the range of the third
sub-data SD3 is expressed as "00000000000000110 . . . ".
[0103] Therefore in the message having the ID of 100, when an error
is detected at the 14th bit of the data section, the break point
discrimination data having "1" at the 14th bit is searched. Because
the 14th bit of the break point discrimination data of the second
sub-data is "1", it is possible to detect that the error has
occurred at the second sub-data. The data section of the message is
rewritten from the 11th bit which is the top bit of the second
sub-data.
[0104] In the above-described construction, with reference to the
break point discrimination data, it is possible to efficiently
execute the sub-data discrimination processing and the rewriting
processing. In addition, it is possible to rewrite the sub-data
into a value selected from the set data D1 and the previously sent
data D2 for each sub-data. That is, even in the same message, it is
possible to rewrite the first sub-data into the previously sent
data and the second sub-data into the set data.
[0105] Because other constructions of the second embodiment and the
operation and effect thereof are similar to those of the first
embodiment, the same parts of the second embodiment as those of the
first embodiment are denoted by the same reference numerals and
symbols as those of the first embodiment.
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